Multilayer rigid container structures, which utilize an oxygen scavenging composition, are known. In the container wall, base polymers such as polyethylene terephthalate have been used along with an oxygen scavenger. The resulting multilayer package wall includes at least an oxygen scavenger core layer as well as inner and outer layers having high oxygen barrier qualities. The oxygen scavenger core layer is a combination of at least an oxygen-scavenging polymer with post consumer-polyethylene terephthalate (PC-PET). The inner and outer layers include at least oxygen barrier quality PET.
Furthermore, multilayer plastic bottles having oxygen-scavenging capacity sufficient to maintain substantially zero or near zero presence of oxygen in the bottle cavity under specified storage conditions have also been disclosed. The multilayer bottle wall has at least three layers. The inner and outer layers are PET or another bottling polyester, which define the bottle cavity and the outside skin of the bottle respectively. Between the inner and outer layers is an oxygen scavenging copolyester layer.
Condensation copolymers used for.making bottles with polyester such as PET or polyethylene napthalate (PEN) have also been disclosed. The condensation copolymers comprise predominantly polyester segments and an oxygen-scavenging amount of polyolefin oligomer segments. The copolymers are preferably formed by transesterification during reactive extrusion and typically comprise about 0.5 to about 12 wt. % of polyolefin oligomer segments. In a preferred embodiment, a bottle is provided having a multilayer wall of at least three layers. The outer and inner layers are of unmodified PET and the oxygen scavenging layer in between the outer and inner layer is made of the condensation copolymers described above having an oxygen scavenging amount of polyolefin oligomers.
A transparent oxygen-scavenging article for packaging oxygen sensitive products is also known, the oxygen-scavenging article having a multilayered wall including at least three layers, an inner and outer layer of biaxially-oriented aromatic polyester polymers such as PET or PEN and an oxygen-scavenging aromatic ester polymer compatible with the polyester polymer. The oxygen-scavenging aromatic ester polymer must include ketone carbonyl groups to provide the oxygen-scavenging functionality and aromatic and ester groups for compatibility with the polyester.
PET containers have been disclosed that have a container wall of stretched plastic material with high oxygen barrier properties and an activating metal incorporated into the plastic material. The plastic material is PET in admixture with a polyamide and the metal is either added to the mixture or contained in one or both of the polymers.
A container containing at least one layer containing a plastics material and ions of at least one metal has also been disclosed. The plastics material in the layer consists of at least a partially split or degraded polyamide which has increased sensitivity to reaction with oxygen in the presence of metal thus giving the layer improved oxygen barrier properties.
A container has been disclosed with a wall having high oxygen barrier properties comprising a molded polymer composition, the composition comprising a granular mixture of (1) a first polymer composition providing strength for the article and (2) a second polymer composition providing strength for the article and (2) a second polymer composition compatible with the first polymer composition. The second polymer composition is obtainable by reacting a polyamide or copolyamide with a solution of a transition metal compound in a volatile solvent under refluxing conditions. The polymer of the first polymer composition can be any polymer and the metal of the metal compound reacted with the polyamide or copolyamide can be any transition metal. The amount of metal in the second polymer composition is at least 500 ppm.
A polymer material having increased sensitivity to reaction with oxygen has also been disclosed, the polymer material comprising a polyamide, which has been reacted with a nucleophilic reagent and possibly an activator. The nucleophilic reagent is selected from the group consisting of compounds containing at least one hydroxyl group, compounds containing at least one alkoxide group, phosphate compounds, pyrophosphate compounds, polyphosphate compounds, salts of organic acids and copolymer of vinyl alcohol and ethylene. The activator is in the form of a hydrogen donor. A process is also disclosed for producing the polymer material, which has increased sensitivity of reaction with oxygen. In the process, a polyamide reacts with the nucleophilic reagent under such conditions that the polymer material is obtained.
Such polymeric containers of PET, PEN and/or polyamide as described above utilize oxidizable components to react with and decrease the amount of oxygen in contact with oxygen sensitive materials packaged in containers. All of these oxidizable materials have the disadvantage of imparting unpleasant odor and/or taste to the packaged materials because of the byproducts given off during the oxidation of the oxidizable materials. Another problem is the uncontrolled oxidation fragmentation from the polymer backbone, which leads to chain secession, thus weakening the physical integrity of the multilayer container structures.
In contrast, the present invention achieves a rigid beverage and food container comprising PET and/or PEN, the container incorporating an oxygen scavenging component of cyclic olefin which does not give off odor and or taste as a result of its oxygen scavenging function. The oxidation also does not cause a change in molecular weight. This is because the cyclic olefin oxygen-scavenging component does not fragment as it oxidizes, thus avoiding the problem of imparting oxidation byproducts to the packaged material while maintaining the structural integrity.
Thus, the present invention overcomes, or at least reduces the effects of, one or more of the aforementioned problems.
Further aspects and advantages of the present invention will become apparent from the ensuing description, which is given by way of example only.